Oligodendrocytes damage in Alzheimer's disease: beta amyloid toxicity and inflammation

Research on Alzheimer's disease (AD) focuses mainly on neuronal death and synaptic impairment induced by beta-Amyloid peptide (Abeta), events at least partially mediated by astrocyte and microglia activation. However, substantial white matter damage and its consequences on brain function warrant the study of oligodendrocytes participation in the pathogenesis and progression of AD. Here, we analyze reports on oligodendrocytes' compromise in AD and discuss some experimental data indicative of Abeta toxicity in culture. We observed that 1 microM of fibrilogenic Abeta peptide damages oligodendrocytes in vitro: while pro-inflammatory molecules (1 microg/ ml LPS + 1 ng/ml IFNgamma) or the presence of astrocytes reduced the Abeta-induced damage. This agrees with our previous results showing an astrocyte-mediated protective effect over Abeta-induced damage on hippocampal cells and modulation of the activation of microglial cells in culture. Oligodendrocytes protection by astrocytes could be, either by reduction of Abeta fibrilogenesis/deposition or prevention of oxidative damage. Likewise, the decrease of Abeta-induced damage by proinflammatory molecules could reflect the production of trophic factors by activated oligodendrocytes and/or a metabolic activation as observed during myelination. Considering the association of inflammation with neurodegenerative diseases. oligodendrocytes impairment in AD patients could potentiate cell damage under pathological conditions.     

Clustering of T cell ligands on artificial APC membranes influences T cell activation and protein kinase C theta translocation to the T cell plasma membrane

T cell activation is associated with active clustering of relevant molecules in membrane microdomains defined as the supramolecular activation cluster. The contact area between these regions on the surface of T cells and APC is defined as the immunological synapse. It has been recently shown that preclustering of MHC-peptide complexes in membrane microdomains on the APC surface affects the efficiency of immune synapse formation and the related T cell activation. Disruption of such clusters may reduce the efficiency of stimulation. We describe here an entirely artificial system for Ag-specific, ex vivo stimulation of human polyclonal T cells (artificial APC (aAPC)). aAPC are based on artificial membrane bilayers containing discrete membrane microdomains encompassing T cell ligands (i.e., appropriate MHC-peptide complexes in association with costimulatory molecules). We show here that preclustering of T cell ligands triggered a degree of T cell activation significantly higher than the one achieved when we used either soluble tetramers or aAPC in which MHC-peptide complexes were uniformly distributed within artificial bilayer membranes. This increased efficiency in stimulation was mirrored by increased translocation from the cytoplasm to the membrane of protein kinase theta, a T cell signaling molecule that colocalizes with the TCR within the supramolecular activation cluster, thus indicating efficient engagement of T cell activation pathways. Engineered aAPC may have immediate application for basic and clinical immunology studies pertaining to modulation of T cells ex vivo.     

Islet-specific expression of CXCL10 causes spontaneous islet infiltration and accelerates diabetes development

During inflammation, chemokines are conductors of lymphocyte trafficking. The chemokine CXCL10 is expressed early after virus infection. In a virus-induced mouse model for type 1 diabetes, CXCL10 blockade abrogated disease by interfering with trafficking of autoaggressive lymphocytes to the pancreas. We have generated transgenic rat insulin promotor (RIP)-CXCL10 mice expressing CXCL10 in the beta cells of the islets of Langerhans to evaluate how bystander inflammation influences autoimmunity. RIP-CXCL10 mice have islet infiltrations by mononuclear cells and limited impairment of beta cell function, but not spontaneous diabetes. RIP-CXCL10 mice crossed to RIP-nucleoprotein (NP) mice expressing the NP of the lymphocytic choriomeningitis virus in the beta cells had massively accelerated type 1 diabetes after lymphocytic choriomeningitis virus infection. Mechanistically, we found a drastic increase in NP-specific, autoaggressive CD8 T cells in the pancreas after infection. In situ staining with H-2D(b)(NP(396)) tetramers revealed islet infiltration by NP-specific CD8 T cells in RIP-NP-CXCL10 mice early after infection. Our results indicate that CXCL10 expression accelerates the autoimmune process by enhancing the migration of Ag-specific lymphocytes to their target site.     

Identification to the species level of <Emphasis Type="Italic">Lactobacillus</Emphasis> isolated in probiotic prospecting studies of human,animal or food origin by 16S-23S rRNA restriction profiling

Background  

The accurate identification of Lactobacillus and other co-isolated bacteria during microbial ecological studies of ecosystems such as the human or animal intestinal tracts and food products is a hard task by phenotypic methods requiring additional tests such as protein and/or lipids profiling.     

Proteome analysis of primary neurons and astrocytes from rat cerebellum

Neurons and astrocytes are predominant cell types in brain and have distinguished morphological and functional features. Although several proteomics studies were carried out on the brain, work on individual brain cells is limited. Generating individual proteomes of neurons and astrocytes, however, is mandatory to assign protein expression to cell types rather than to tissues. We aimed to provide maps of rat primary neurons and astrocytes using two-dimensional gel electrophoresis with subsequent in-gel digestion, followed by MALDI-TOF/TOF. 428 protein spots corresponding to 226 individual proteins in neurons and 406 protein spots representing 228 proteins in astrocytes were unambiguously identified. Proteome data include proteins from several cascades differentially expressed in neurons and astrocytes, and specific expressional patterns of antioxidant, signaling, chaperone, cytoskeleton, nucleic acid binding, proteasomal, and metabolic proteins are demonstrated. We herein present a reference database of primary rat primary neuron and astrocyte proteomes and provide an analytical tool for these structures. The concomitant expressional patterns of several protein classes are given and potential neuronal and astrocytic marker candidates are presented.     

Reversible and strong immobilization of proteins by ionic exchange on supports coated with sulfate-dextran

New and strong ionic exchange resins have been prepared by the simple and rapid ionic adsorption of anionic polymers (sulfate-dextran) on porous supports activated with the opposite ionic group (DEAE/MANAE). Ionic exchange properties of such composites were strongly dependent on the size of the ionic polymers as well as on the conditions of the ionic coating of the solids with the ionic polymers (optimal conditions were 400 mg of sulfate-dextran 5000 kDa per gram of support). Around 80% of the proteins contained in crude extracts from Escherichia coli and Acetobacter turbidans could be adsorbed on these porous composites even at pH 7. This interaction was stronger than that using conventional carboxymethyl cellulose (CMC) and even others such as supports coated with aspartic-dextran polymer. By means of the sequential use of the new supports and supports coated with polyethyleneimine (PEI), all proteins from crude extracts could be immobilized. In fact, a large percentage (over 50%) could be immobilized on both supports. Finally, some industrially relevant enzymes (beta-galactosidases from Aspergillus oryzae, Kluyveromyces lactis, and Thermussp. strain T2, lipases from Candida antarctica A and B, Candida rugosa, Rhizomucor miehei, and Rhyzopus oryzae and bovine pancreas trypsin and chymotrypsin) have been immobilized on these supports with very high activity recoveries and immobilization rates. After enzyme inactivation, the protein could be fully desorbed from the support, and then the support could be reused for several cycles. Moreover, in some instances the enzyme stability was significantly improved, mainly in the presence of organic solvents, perhaps as a consequence of the highly hydrophilic microenvironment of the support.     

UniProt archive

UniProt Archive (UniParc) is the most comprehensive, non-redundant protein sequence database available. Its protein sequences are retrieved from predominant, publicly accessible resources. All new and updated protein sequences are collected and loaded daily into UniParc for full coverage. To avoid redundancy, each unique sequence is stored only once with a stable protein identifier, which can be used later in UniParc to identify the same protein in all source databases. When proteins are loaded into the database, database cross-references are created to link them to the origins of the sequences. As a result, performing a sequence search against UniParc is equivalent to performing the same search against all databases cross-referenced by UniParc. UniParc contains only protein sequences and database cross-references; all other information must be retrieved from the source databases.     

Novel proteomic approaches for tissue analysis

Proteomics, the global study of protein expression and characteristics, has recently emerged as a key component in the field of molecular analysis. The dynamic nature of proteins, from ion channels to chaperones, presents a challenge, yet the understanding of these molecules provides a rich source of information. When applying proteomic analysis directly to human tissue samples, additional difficulties arise. The following article presents an overview of the current proteomic tools used in the analysis of tissues, beginning with conventional methods such as western blot analysis and 2D polyacrylamide gel electrophoresis. The most current high-throughput techniques being used today are also reviewed. These include protein arrays, reverse-phase protein lysate arrays, matrix-assisted laser desorption/ionization, surface-enhanced laser desorption/ionization and layered expression scanning. In addition, bioinformatics as well as issues regarding tissue preservation and microdissection to obtain pure cell populations are included. Finally, future directions of the tissue proteomics field are discussed.     

Selection for human immunodeficiency virus type 1 recombinants in a patient with rapid progression to AIDS

Although human immunodeficiency virus type 1 (HIV-1) recombinants have been found with high frequency, little is known about the forces that select for these viruses or their importance to pathogenesis. Here we document the emergence and dynamics of 11 distinct HIV-1 recombinants in a man who was infected with two subtype B HIV-1 strains and progressed rapidly to AIDS without developing substantial cellular or humoral immune responses. Although numerous frequency oscillations were observed, a single recombinant lineage eventually came to dominate the population. Numerical simulations indicate that the successive recombinant forms displaced each other too rapidly to be explained by any simple model of random genetic drift or sampling variation. All of the recombinants, including several resulting from independent recombination events, possessed the same sequence motif in the V3 loop, suggesting intense selection on this segment of the viral envelope protein. The outgrowth of the predominant V3 loop recombinants was not, however, associated with changes in coreceptor utilization. The final variant was instead notable for having lost 3 of 14 potential glycosylation sites. We also observed high ratios of synonymous-to-nonsynonymous nucleotide changes-suggestive of purifying selection-in all viral populations, with particularly high ratios in newly arising recombinants. Our study, therefore, illustrates the unusual and important patterns of viral adaptation that can occur in a patient with weak immune responses. Although it is hard to tease apart cause and effect in a single patient, the correlation with disease progression in this patient suggests that recombination between divergent viruses, with its ability to create chimeras with increased fitness, can accelerate progression to AIDS.